If you can give me remote access(VNC, SSH) to this RPi system, I might be able to have a look and give it a try.
I didn't want to waste expert time on a problem that I thought was probably my finger trouble. What do you suggest to run FPCupdeluxe on a 64 bit arm platform given the following?
To recap and confirm, my Pi400 was shipped with a 32 bit OS that ran fpcupdeluxe-arm-linux but gave errors for missing packages. When I downloaded the latest RPiOS it loaded as 64 bit and fpcupdeluxe-arm-linux as expected wouldn't run but At that point I didn't realise the RPiOS had changed word size. Having some time this morning between looking after my mum 24/7 in her 1 bedroom flat amongst the medical equipment I checked the new RPiOS as suggested.
/bin/dmesg: ELF 64-bit LSB pie executable, ARM aarch64, version 1 (SYSV), dynamically linked,
interpreter /lib/ld-linux-aarch64.so.1,
BuildID[sha1]=30049d6b3eae41a41b4f08f206d80b7ee42afdac, for GNU/Linux 3.7.0, stripped
Reading this
AARCH64-Linux IS supported by fpcupdeluxe. No problems there, I think, but I have only RPI4's, not a 400.
I downloaded fpcupdeluxe-aarch64-linux to see if it would run and it did for over 40 minutes then gave this error followed by others obviously.
gcc: error: unrecognized command-line option ‘-m64’
At least I have kicked the can further down the road.