Earlier quoted context omitted.
If you'd ever get the raw data, you can use RTKLIB* for RTK/PPK. Ublox chips stream the raw data, if you configure it to do so. * https://github.com/tomojitakasu/RTKLIB
Using rtklib like that with ublox modules was actually the common norm for affordable precision enhancement on a single band at the time of the ublox M8 family, before the era of dual band modules (such as the ublox F9 family), because you could still get relatively cheap modules that didn't have integrated RTK but gave you the raw data so that you could do it externally with RTKLIB. But single-band only i.e. not the…
just to avoid any misunderstanding: by "you don't even get decent dual-band GNSS receivers that output raw data but don't have integrated RTK like in ublox M8 times" I meant… "like in ublox M8 times" for single band.