Having the same problem, updated to 4.10.1, no longer getting graphs.
● weewx.service - LSB: weewx weather system
Loaded: loaded (/etc/init.d/weewx; generated)
Active: active (running) since Wed 2023-02-01 11:19:48 MST; 1 day 20h ago
Docs: man:systemd-sysv-generator(8)
Process: 10018 ExecStart=/etc/init.d/weewx start (code=exited, status=0/SUCCESS)
Tasks: 2 (limit: 4915)
CGroup: /system.slice/weewx.service
└─10057 python2 /usr/share/weewx/weewxd --daemon --pidfile=/var/run/weewx.pid /etc/weewx/weewx.conf
Feb 03 08:05:16 RPi python2[10057]: weewx[10057] ERROR weewx.reportengine: **** File "/usr/share/weewx/weewx/reportengine.py", line 180, in run
Feb 03 08:05:16 RPi python2[10057]: weewx[10057] ERROR weewx.reportengine: **** obj = weeutil.weeutil.get_object(generator)(
Feb 03 08:05:16 RPi python2[10057]: weewx[10057] ERROR weewx.reportengine: **** File "/usr/share/weewx/weeutil/weeutil.py", line 1335…n get_object
Feb 03 08:05:16 RPi python2[10057]: weewx[10057] ERROR weewx.reportengine: **** mod = __import__(module)
Feb 03 08:05:16 RPi python2[10057]: weewx[10057] ERROR weewx.reportengine: **** File "/usr/share/weewx/weewx/imagegenerator.py", line 259
Feb 03 08:05:16 RPi python2[10057]: weewx[10057] ERROR weewx.reportengine: **** log.error(f"Unknown plot type {plot_type}. Ignored")
Feb 03 08:05:16 RPi python2[10057]: weewx[10057] ERROR weewx.reportengine: **** ^
Feb 03 08:05:16 RPi python2[10057]: weewx[10057] ERROR weewx.reportengine: **** SyntaxError: invalid syntax
Feb 03 08:05:16 RPi python2[10057]: weewx[10057] ERROR weewx.reportengine: **** Generator ignored
Feb 03 08:05:16 RPi python2[10057]: weewx[10057] INFO weewx.reportengine: Copied 0 files to /var/weewx/reports
Ed