Devuan recommends using deb.devuan.org in your /etc/apt/sources.list to select where you get your Devuan packages from.  The name deb.devuan.org is a DNS round robin, which means that when you try to access it you will be sent to one of the mirrors that are part of it.  None of those mirrors have an HTTPS certificate that matches "deb.devuan.org", but likely have their own HTTPS certificate, due to the security issues involved in letting lots of people have a copy of a security certificate.  So all use of deb.devuan.org must be done via HTTP, as using HTTPS will result in errors.

If you do wish to use HTTPS, you should instead directly use one of the mirrors that supports HTTPS.  https://pkgmaster.devuan.org/mirror_list.txt lists all the mirrors, what protocols they support, and where they are located.  So you can pick a nearby mirror.

Previously it had been suggested that people use country codes for packages, for example us.deb.devuan.org for users in USA.  That is now no longer the case, country codes are no longer likely to work.

apt-panopticon is a script that regularly checks the health of the entire Devuan mirror system.  The results of that script are currently available on two servers.  https://borta.devuan.dev/apt-panopticon … t-web.html which checks the mirrors once an hour, though it is currently having timeout problems which are being investigated.  https://sledjhamr.org/apt-panopticon/re … t-web.html which checks every ten minutes.

With large parts of the world working from home as part of COVID-19 lockdowns, the Internet is being used more than is usual.  So there tends to be more random network issues.  Any particular network issue might be at your end, at the other end, or somewhere in between.  As mentioned above, even our own infrastructure is having some minor issues every now and then.

Please have patience, and stay healthy.