There's a particular problem in Devon with a relatively large number of unsurfaced roads known locally as 'green lanes' and marked on the ground as Unmetalled Road or just County Road: technically motor vehicles do have a right of way, but in practice they are usually impassable without a four-wheel-drive and frequently completely impassable. This particular track is shown on OS maps as having public access, but it isn't on the local Public Rights of Way list, suggesting that it is one of those roads. When lockdown ends I'll check the status of this track/road and update its tags.