Hi there

While universe@home is down, I added mlc@home to my computers:

1) Desktop - Windows 10 - Boinc 7.16.20 - GenuineIntel Intel(R) Core(TM) i3-7100 CPU @ 3.90GHz [Family 6 Model 158 Stepping 9](4 Prozessoren)
2) HP T620 - Linux Ubuntu 21.10 - Boinc 7.16.17 - AuthenticAMD AMD GX-217GA SOC with Radeon(tm) HD Graphics [Family 22 Model 0 Stepping 1] (2 Prozessoren)
3) Raspberry Pi 3 - Linux Raspbian GNU/Linux 10 - Boinc 7.14.2 - ARM ARMv7 Processor rev 4 (v7l) [Impl 0x41 Arch 7 Variant 0x0 Part 0xd03 Rev 4] (4 Prozessoren)

While #1 & #3 get Tasks, #2 don't... ...can someone explain to me why it happen ?

Both, the Raspian and the HP T620, don't have graphic displays and work 24/7 only for Boinc.
Universe@home works fine on all computers and all three get tasks... ...as long as the server don't crash... ;)

I'd first check that you have a 64bit Ubuntu install and not a 32bit.

Unfortunately my ideas run out there. Best of luck