I was able to create FPC3.1.1 source and executable packages for packagemanager, and also Lazarus 2.1.0 as executable package. I installed them and my program works OK with that. I have included the updated termios in the FPC packages.
I have to say without copying the file structures s40in has inside his packages I would not have been able to pull this off. He’s very knowlegdeable in my eyes 
Thanks!
I only did the 64bit versions, and I’ll leave it at that for now.
I also updated FPC 3.2.0 source and executable packages that work with the already existing Lazarus 2.0.2 package, also with updated termios.
Update:
Just uploaded it all in two zip files:
http://www.rudolfs-place.nl/Haiku/Downloads/FPC_320_Lazarus_202-x86_64.zip
and
http://www.rudolfs-place.nl/Haiku/Downloads/FPC_331_Lazarus_210-x86_64.zip
Both these files contain the mentioned versions of:
- FPC sources + termios,
- FPC binaries + termios,
- Lazarus binaries,
- LibQt5Pas pascal bindings,
- multiplatform version of SynaSer.
Update: please note that in Synaser the commented out ‘Purge’ command contains a mistake which of course is not active as it’s commented out. Anway, when the tty driver in Haiku is updated you can enable the purge command again, but the line should read:
SerialCheck(TCFlush(FHandle, TCIOFLUSH));
In my app it’s working OK that way
For the tty driver update status see: https://review.haiku-os.org/c/haiku/+/2516
Hopefully I did it right (enough) so it indeed works on everyone’s recent 64-bit Haiku installations…