I've used the following workaround:
- created old style <ppa-name>.list file for to-be-purged ppa
``` deb https://ppa.launchpadcontent.net/oibaf/graphics-drivers/ubuntu/ mantic main ```
- deleted new style <ppa-name>.source
and ppa-purge worked like a charm
I've used the following workaround:
- created old style <ppa-name>.list file for to-be-purged ppa
``` /ppa.launchpadc ontent. net/oibaf/ graphics- drivers/ ubuntu/ mantic main
deb https:/
```
- deleted new style <ppa-name>.source
and ppa-purge worked like a charm