I don't have experience with OpenBSD and NetBSD, but for FreeBSD, dual-booting with Linux should be relatively straightforward.
I guess your issue is a mismatch between BIOS/MBR and EFI/GPT partitions tables. In "guided" partitioning, FreeBSD uses GPT exclusively. If you had installed Linux first on a MBR, it won't work and you have to go in manual partitioning. You only need a single partition (FreeBSD calls them slices), and then you can sub-partition that slice (typically for a simple setup, a few GB in
If you install FreeBSD first, Linux should gladly accept GPT.
If, for some reason, you use MBR but your disk once contained a GPT, the FreeBSD installer can get confused by a secondary GPT at the end of the disk (at least it was in FreeBSD
You might also want to modify your BIOS settings and choose (U)EFI boot method instead of BIOS/Legacy (if available).