Ubuntu 20.04

[Dirk Broer]

Linux Mint is for now 'safe' as it (Mint 19.x) is based upon Ubuntu 18.04, for which the GPU troubles were solved once kernel 5.x arrived (with as result that a much broader range of AMD GPUs became productive, e.g. the IGPs of my socket AM1 Athlon's), though you may have to use the Oibaf PPA for crunching-capable OpenCL drivers. CAL has stopped being supported since Ubuntu 16.04., leaving some pretty good cards useless. Out-of-the-box present Ubuntu will at best use the Open Source AMDGPU driver (and otherwise the Open Source Radeon driver), which is not accompanied by the files needed to crunch being enabled -and those files give the error mentioned when enabled by means of choosing the Oibaf drivers.
OpenCL, for us crunchers a must-have, seems utterly unimportant for gamers and 'normal' users and testing a new release seems to be done with only the general user in mind -which is not us, crunchers.

Ubuntu 20.04 system requirements

• 2 GHz dual core processor.
• 4 GiB RAM (system memory)
• 25 GB of hard drive space (or USB stick, memory card or external drive but see LiveCD for an alternative approach)
• VGA capable of 1024x768 screen resolution.
• Either a CD/DVD drive or a USB port for the installer media.
• Internet access is helpful.

When it comes to have systems running that do not meet the requirements, without GPU and GUI, you should consider FreeBSD.
I think that you can safely upgrade your server(s), without GPU and GUI, to Ubuntu 18.04 though. Ubuntu 18.04 LTS has normal LTS support for five years, until April 2023 and has paid ESM support available from Canonical for an additional five years, until April 2028. My guess is that by 2023 the problems with 20.04 are sorted out -which are OpenCL GPU problems, so not applicable to your situation anyway.