With my more recent builds (of IodéOS and LineageOS4microG) for lilac, I started to encounter the mobile data problems that have been reported previously on LOS-based ROMs for this device . Specifically, some sites and some apps which access the internet were working fine when connected via WiFi, but failing or timing out when connected via mobile data, even though the phone was showing a good 4g connection.
My network provider is Your Co-op, a UK MNVO which uses the EE network
The ‘fix’ that worked for me was to edit the EE Internet APN, changing APN type to default instead of default,supl. (I recall that I had to add the ,supl a couple of years ago to fix a similar problem). I don’t know why the problem started to occur for me, or why the ‘fix’ works, but I hope my experience might help any others who may be encountering a similar problem.