The irony is that you can run these Level 2.5 text services into many UK TVs now and they decode them fine, as do the built in teletext decoders in some free-to-air satellite receivers. Although take-up across Europe has been very low, manufacturers did start to implement them.
With a Raspberry Pi and the right software you can get your Pi to output, via the composite video output (on a phone on the first gen models and then on a 3.5mm composite+audio jack on more recent models, or a PCB header on the Zeros), teletext in vertical blanking with no additional hardware. This includes Level 2.5 support
There's quite a scene involved in 'DIY Teletext' - including people taking the BBC News website RSS feeds etc. and creating 'CEEFAX' from them - though the retirement of Digital Text may mean that the end of headline character limits make this trickier.