HP Elitebook 845/855 AMD support 32GB RAM officially, but they have 2 SODIMM slots so theoretically should support 64GB. One thing to watch out with Linux on HP laptops with AMD currently are problems with standby mode. They lack S3 deep sleep power state - only provide S2Idle so called Modern Standby. Although there are ways to mod ACPI tables there is still some black screen issue when the return from suspend happens - search stories on Reddit. I hope constantly improved Linux kernel will bring some workarounds and HP will do more Linux testing too on their quite decent HW specs.

I finally decided to go with proven option and ordered Lenovo T14 with 48GB RAM. It works flawlessly with Linux 5.8 because Lenovo added "legacy" S3 power state mode toggle in BIOS setup specially for non-Windows OSes.