JP1 Remotes

I recently bought this very cheap USB <-> UART adapter, it works perfectly with RMIR.
The only point is that RTS is not available on the main 6 pins connector (only DTR is available in addition to TXD and RXD on this connector) but it is available as one of the 8 additional signals (holes on the sides), so you will need to solder a pin on the corresponding hole to use it with RMIR.

https://www.wish.com/product/58e5181d16 ... ?share=web

The Wish item is $4.90 with tax and shipping from China (now sold out)

There is a CP2102 on eBay for $4.20 shipped from the US.
https://www.ebay.com/itm/133321753393

From China it's only $1.12
https://www.ebay.com/itm/284022352349

By way of comparison, you can get a 6Pin PL2303HXD cable, where all you need is a new 2*3 Dupont header, from China for $4.37
https://www.ebay.com/itm/163746659403

There is a FTDI FT232RL USB cable for $5.46 from China
https://www.ebay.com/itm/303670632779

Or you could get an FTDI card where you would need to add the cable, for $2.27
https://www.ebay.com/itm/362500608866

As for the Dupont headers, which you would need for the CP2102 also, you can get 20 of them for $3.39 shipped from China.
https://www.ebay.com/itm/152681689398