Reading here [1] and using the patch mentioned here [2] I was able to
get apcupsd running on 12.1 to correctly report data from a BE600M1.
Also, some functions in apctest now work as well.
[1] https://sourceforge.net/p/apcupsd/mailman/apcupsd-users/thread/CAMe0L0Vc9BzCYehm-bZUoPgHaL-43xsjetQ3hi7gD380b7NsqQ%40mail.gmail.com/#msg36287119
[2] http://apcupsd-ups-control-software.10985.n7.nabble.com/Potential-bug-with-USB-driver-and-HID-reports-td10001.html#a10043
Testing current apcupsd reporting via apcaccess had limited data. With the 2017 patches [1] this appears to have fixed this issue with USB I/O issues.
I don't know how this patch plays with other APC USB attached UPS. I can't fully vet the cpp from the patches but it at least fixes my issue with the BE600M1.