It doesn't sound real encouraging but thanks.

edit:

I've had a look at the link you suggested, and did a search for "ESP32 module with display", which turned up some pricey ($150-ish) options along with a bunch of cheaper Arduino semi-equivalents ($20-ish).  The linked text mentioned that it used a standard open-source distro, which i fear will be some ubuntu flavor that uses system-d and i ain't going there no more, but this may be blind prejudice on my part, and they didn't *say* what distro...

The Moto Z4 (which i purchased mostly for the Hasselblad camera mod, and the Z4 seems (to me) like a fairly useless device since it has no bezels and capacitive touch is so jacked up it's almost impossible to control) has some onboard processor or other which seems like another possible alternative, if one wants to produce a Mod and wed himself to the phone; I'm fairly certain that i don't, i'm not even buying their camera Mod because the thing is too touchy to use imo, and the in-screen fingerprint sensor is both slow and stupid.

One thing i didn't mention is that for the various products i have in mind, i want to keep the parts-list simple enough that Joe Average-ish can buy the parts and build his own, as much as possible; i figure that should put a cap on the prices people have to pay for copies, since if having it made is too much one can build it himself.

Since i already have the Arduino to learn from, i'll see how far i can take the first project, which is a battery-string-controller.  The two-way communication issue is the one i expect to be the deciding issue.

Thanks again, i appreciate the assist.

I'll be setting up a couple of dual-boot microSD cards today, if these unopened packages on my desk contain a WIFI card that actually works with both linux and Windows-10, and the storage cards i ordered.  It'll probably take a couple hours, but once you get it set up, it's a matter of using it.

I cheat.  Maybe that's my themesong lol.  Here is how i do it:

1. write a new ms-dos partition table to empty media.

2. quiesce all the OS's on your source system that you want to include.  for example, i run Devuan-ascii and Debian-jessie along with Ubuntu-oneiric.  Jessie is my go-to for this kind of operation... not that i can't use Devuan-ascii for it, but Devuan is my go-to OS for normal use, so it's easier if i run jessie to copy the quiesced Devuan partition, then reboot and use Devuan to copy jessie and oneiric onto the target media.

3.  run gparted or equivalent, to see how much space you need on the target media.  create the partitions at this point.  generally what i do is allocate 15gb for Devuan since it's still in daily use and may need more space.  If memory serves, i allocate 10g for jessie and 6g for oneric.  It's a matter of your usage.  I keep all of my user-data in a separate partition, and use a bind-mount in fstab to hook things up.

4.  make sure that you create at least 2 *primary* partitions, or create one and leave space for another.  there are some systems, forex the Dell xps-13, which are "windows-intended" so to speak, and their BIOS plays hardball with the Windows rue about booting only from a primary partition.  Once i have a primary partition of Devuan-ascii, and space left for ceres or whatever when it goes stable, i make the
remainder of the media into an extended partition.  In the extended partition are any other OS's (in my case oneiric) and partitions for my data.

5.  once you have your partitions laid out (this all takes about 10 minutes so far), pick a primary OS.  copy the quiesced OS to the new media (i use rsync because file-by-file is faster than dd etc, and probably always will be unless your partition is maybe 90% full.

6. after you've copied all your installed-and-running (but quiesced) OS, or multiple OS's and data partitions, you're 75% of the say there.

7.  the next step is to edit the copied /etc/fstab files.  use the UUID option to identify partitions, not dev-name or label; UUID is most unique and least problem-prone.

8.  in addition to fstab, you also need a swap partition to act as a suspend/resume device.  You need to put its UUID in the fstab for that OS so it doesn't hang up forever on boot while it times out waiting for the suspend/resume device which it won't find because you never assigned/updated it.  (bug, in startup, imo).  offhand i forget the filename that has to be updated (there are at least 2 different ones based on OS) something like blah/blah/resume.conf  Then you need to update initramfs so the booting OS can find the suspend/resume info.

9.  at this point it's a matter of hooking up grub.  imo grub sucks.  i wrote utilities years ago to do all this crap.  Whatever; it can be done manually, but it's nice to be able to get all your device information placed in the clipboard by poking one key, etc.

Of course if you want to fiddle with grub and its os-probes, the previous replies might probably do the job; i gave up on using the regular grub procedures years ago, because imo they are garbage.

Hey, i'm old and prejudiced, and i've done this "set up a multi-boot" thing more than a few times over the past 10 years or so.  Good luck, you'll figure it out with some help from your friends.

Please explain why this is considered acceptable?

Devuan build procedures were inherited from whoever, the whole distribution and install process is a mess imo, we should be installing ALL drivers on a test system, along with a minimal set of core components like synaptic, which will let even android-iots get things up and running, but nobody has time to rewrite it all or try something new, this being largely a spare-time effort, if you get my drift?  ...and once the test system is up and running, put a snapshot of the ext4 filesystem into an iso file.  that way you get exactly what was tested, and if it doesn't work you can choose a regressed snapshot left laying aorund from when it was unstable.  But hey, it is what it is, and it's getting better imo. 

As for your particular situation... if i knew how to convert the entire contents of a hard-drive into an iso, i could make up a system for you from my krud in a couple hours or so, if i had time to do it.  Time's the thing, time's what's being stolen from every employee.  Sorry for the digression, let me know if i can help.  btw, the system i'm talking about is currently running just fine on a Lenovo t510.  The model you're talking about may differ in terms of chipsets and drivers.  Best luck.

Isn't that interesting.  Seeing as how i'm logged in through an android tablet atm, it's a bit tough to grab a screenshot from my linux system... and you could very well be correct, i'm not sure how "default" it was when it presented the rat icon.  Of course by the time i'm done doing android-stuff and get back to my linux box, i'll no doubt have forgotten about snagging a screenshot.  so it goes.

btw, i've determined since my last post (above) that Devuan ascii does not contain the drivers needed for the Lenovo 300e's stock wifi card  (Intel 8265ngw).  The details are perhaps forgotten, but i think the Intel drivers for that wifi chip don't appear in the kernel until something like version 5.26, and given my experience  installing drivers for broadcom wifi and intel graphics on a a Dell XPS13... i decided it would be easier to just replace the wifi chip with an intel 7260 which is listed as a valid FRU in the Lenovo hardware manual and supposedly supported in the current ascii kernel.  Theoretically that chip is now waiting at the post-office, so we'll see how that goes.

I'm of the opinion (FWIW) that it would be very useful if the Devuan builds included all the currently released proprietary drivers as soon as they become available, rather than waiting months/years for the kernel that contains them.  Of course it may be a matter of what's been tested with which kernel containing what changes, but i'm not gonna wait around for a 5xx kernel release when Devuan is on 4xx and the only obstacle is a wifi driver, maybe i'm an outlier on this, who knows.

(Is there a way to delete an unused account from this site?  i'm really not cranky anymmore.)