As other people tried this also How to install arm-none-eabi-gdb on Ubuntu 20.04 LTS (Focal Fossa) i found that the universe repo has a pretty much working toolchain. I've tested it.
hoo2@shirka:~$ apt list *-none-eabi* --installed
Listing... Done
binutils-arm-none-eabi/focal,now 2.34-4ubuntu1+13ubuntu1 amd64 [installed]
gcc-arm-none-eabi/focal,now 15:9-2019-q4-0ubuntu1 amd64 [installed]
libnewlib-arm-none-eabi/focal,focal,now 3.3.0-0ubuntu1 all [installed]
libnewlib-nano-arm-none-eabi/focal,focal,now 2.11.2-1 all [installed]
libstdc++-arm-none-eabi-newlib/focal,focal,now 15:9-2019-q4-0ubuntu1+12build2 all [installed]
The problem is that for "some" reason the package contains all the utilities from here but NOT the gdb executable.
Is that intended? If you manually download (only arm-none-eabi-gdb file) and copy to /usr/bin/ its working fine!
This seams not logical to me as this way, gdb is not updated with apt updates :(
Does anyone knows about this? What is the official way of installing gdb?