After updating both my PC's with intel-915 graphics they fail to resume. They wake up, the screen wakes but no graphics, the whole system is then locked requiring a hard reboot. No journal output after last entry of "suspending". No problem with kernel on AMD system.

The journal will have output from the broken wake up after reboot. just check the full journal output, and go to the time-frame the failed resume happened. (and FWIW, no issues here on intel and 5.10.4)

End of journal

Jan 02 14:36:50 Airtop3 systemd[1]: Reached target Sleep.
Jan 02 14:36:50 Airtop3 systemd[1]: Starting Suspend...
Jan 02 14:36:50 Airtop3 kded5[1210]: networkstatus: SolidNetwork changed status: 0
Jan 02 14:36:50 Airtop3 kded5[1210]: networkstatus: "SolidNetwork" , 0
Jan 02 14:36:50 Airtop3 systemd-sleep[18310]: Suspending system...
Jan 02 14:36:50 Airtop3 kernel: PM: suspend entry (deep)
Jan 02 14:36:50 Airtop3 kernel: Filesystems sync: 0.005 seconds

Will try some more.
Tried again with reboots etc. Identical journal output.

Did you use 5.10.3 (thus linux-next)? Or just using the build repo, and this is the first install of 5.10?

5.10.3 next as far as I know. Not there at the moment.
Edit. Definitely 5.10.3-1 previously, no problems.

Is your system using an HDMI cable to connect to a monitor? Possible to test with DVI or VGA Cable?

One PC has a HDMI to VGA adaptor, the other is Display Port. Both experience the same problem.
Will try a HDMI in place of the DP cable tomorrow.

Edit: Same with HDMI
kernel linux 5.10.4.arch2-1 on arch system (same machine) resumes OK. Will try arch on other PC.