I would also love to be able to ship recent Linux versions in all cases, but as of sadly common practice of many SoC and SBC manufacturers, to not produce open source hardware/firmware/drivers, and to provide own outdated kernel versions with driver and firmware blobs instead of contributing those upstream in the first place, often SBCs are not (fully) functional with upstream and Debian Linux versions.
However, I fully understand the decision to not put efforts in "supporting" this manufacturer behaviour.
Interesting is, that I now successfully solved it by creating the /sbin/mount.exfat => mount.exfat-fuse symlink. I though I tested this already, without success. That seems sufficiently simple. When the kernel modules becomes available later and exfat-fuse it purged, even leaving the symlink pointing to nowhere in place does not break mounting exfat filesystems with the native Linux driver, so it is quite save to create it, when stuck with an old Linux version:
------- ln -s mount.exfat-fuse /sbin/mount.exfat ------- Best regards, Micha