The only other option that I can think of would be ripping your discs and have Kodi play the on an Nvidia Shield...

I owned 2 Samsung BRPs and both could convert DTS to DD5.1 on the fly.   I think the UHD models could do so too, but I cannot promise that.  The manuals must be online somewhere if you want to research further.

Then you just have to find one.  Samsung stopped making BRPs a couple of years ago.  That in itself tells a story, I think, but you may be able to pick one up on eBay.

Thanks so much everyone - I suspect Samsung is the route to go down I will have a look on FB marketplace and also eBay. 

I believe the Samsung UBD-M9500 was the latest UHD player from Samsung that could re-encode DTS to Dolby Digital 5.1.

I’ve just added a Beam to my home office for ~5.0 surround sound, moving my Play 1’s to the rear, and I quickly discovered the DTS limitation of a Sonos system (all my BRD viewing is with a traditional wired receiver based 7.1 system so there no reason I would have noticed until now). This system is primarily intended to play surround sound music, and it works very well (with DD 5.1 input), the Beam does a great job of pushing the front channels into the corners of the room, as if they were coming from discrete speakers.

With Samsung having exited the BRD business, it seems Sony is now the only option for a BRP that converts DTS to DD 5.1. I picked up the BDP-S3700 at my local Best Buy for only $80 (regular price) and it works perfectly with my DTS-HD MA audio Blu-Rays, providing 5.1 audio to my Beam (there is no DD audio on these discs), although it will not play a DTS encoded CD, but I only have one of those. I haven’t yet tried Blu-Ray discs or DVDs with DTS soundtracks, but I no reason to believe they wouldn’t work. 

If you need a 4k player, Sony’s UBP-X800M2 has the same DTS conversion capability according to other posts on this and other forums, and is also widely available from the same store for $300.

Fianlly, the Xbox is supposed to convert DTS as well, but I had no interest in getting one, and all models appear to be sold out everywhere.

No need to pay too much for a used Samsung on eBay, get a Sony!

You should be able to pick up a used Xbox One as folks upgrade to the new Xbox Series models, and all Xboxes transcode DTS to DD 5.1. (Well you’ll need one with a disc drive of course).