Does it?

For whatever reason, you seem to have have generated a size issue in the drive, apparently [root] which the OS reports being full.

Maybe your "small SSD" SDD is indeed too small for what you are attempting to do.
Maybe your partitioning is not the right one for a drive that small.

That said, bear in mind that you are on a [testing] release.
As such, it is usually/always problematic.

Boot with [gparted] live, open a terminal and run df to see "what is where" so to speak.
See what space [/home] and [/var/log] are using/have available and delete whatever you do not need to try to improve the situation.

Nuke a file named [.xsession-errors] usually found in [/home].

You may be able to boot after cleaning up all that.

A.

booted into windows and downloaded a trial of extfs for windows and saw that there are in fact already 8,76 something GB available to me;
booted back into Linux, back online, could boot into GUI.

more false alarm than a real calamity; glad could save a 50-60 euro for a bigger nvme (for now).
also, the windows 10 could receive another year of updates until october 2027, so the laptop could still be useful ( i like dual-boot).

was however needed to forcefully remove a file that "empthing trash via icon was not able to empty.

[¬fait accompli`~]

EDIT:

it seems there is still a bit confusion on the free space;

here it says / 9,022 MB available

Installing:
  trash-cli

Summary:
  Upgrading: 0, Installing: 1, Removing: 0, Not Upgrading: 182
  Download size: 52.8 kB
  Space needed: 324 kB / 9,022 MB available

Get:1 http://deb.devuan.org/merged freia/main amd64 trash-cli all 0.24.5.26-0.3 [52.8 kB]
Fetched 52.8 kB in 0s (108 kB/s)     
Selecting previously unselected package trash-cli.
(Reading database… 571098 files and directories currently installed.)
Preparing to unpack …/trash-cli_0.24.5.26-0.3_all.deb…
Unpacking trash-cli (0.24.5.26-0.3)…
Setting up trash-cli (0.24.5.26-0.3)…
Processing triggers for man-db (2.13.1-1)…

however, the kparted says there is more space?

https://ibb.co/qLDgDfXf

i don't think there is anything to resize, since do the "automaticl" installer most of times, which does 1 small EFI, 1 home-everything-else, 1 swap-1GB if rememeber correctly, but things might have changed in the meantime.

there was a suggestion to delete directories in trash via terminal in like in

rm -rf ~/.local/share/Trash/*

but there is no such directory; i use KDE on this laptop;

EDIt: on second thought, it sounds a good advice, i could bootinto gparted live and resize the swap or delete it; that could do the trick.
but hopefully such situation could be amended also otherwise?

You may want to consider making a back-up image of the drive (just in case) and then booting via a [gparted] *.iso to first do a full check on the drive and then resize whatever partition is complicating things, probably /.

Best,

A.

have a small SSD on which sits Devuan Testing,
so far if function deceently, however am prone to download things and not always tidiing up in time;

now have run into impasse;

the OS complained running out of space (root is 0 Byte or similar), so i kept deleting things, kept emptying Trash; but it seemed to have made no effect;

now, thought that a reboot will probably clear up the space since have "deleted" quite some files;
but apparently it did not;
"Free" command still reports 0 swap;
and i am no longer able to login to GUI;

when i boot into recovery-mode; i am still deleting files, but apparently the situation does not change;
the remaining space is "0";

would kindly ask who i ccould empty the trash via terminal? if it is even still possible at this point;

tried to install "trash-cli" for "trash-empty" but it would not function, ince 324KB are not available;
it is a bit comical since i really did delete quite some files + also emptied the trashcan prior to rebooting; but apparently it was already too late since the root going down to 0 Byte or what? must have prevented things.

Would be glad if this could still be salvaged,
thanks.