I have this transmitter/receiver so I will address the bad reviews - READ BELOW BEFORE PURCHASING.
I also previously got the Bonelk USB hub which turned out great so I think this is worth it for $24, similar in price to cheaper options on Amazon. https://www.ozbargain.com.au/tag/bluetooth-transmitter
It uses microUSB charging (I know this is important for many of you so here it is at the top).
This Bonelk Bluetooth adapter has "Airpods/Airpods Pro compatible" written on the box. Which tells me it uses the AAC bluetooth codec, which is what I wanted because my over ear headphones support it and it means lower latency than SBC.
Important: If your headphones do not have AAC codec in the specifications, as stated in multiple bad reviews this transmitter may not connect to them!
I can see a few bad reviews on TGG and other stores that say their headphones were unable to connect. Most likely their headphones did not support AAC codec and this is why. (e.g. one review says their new Sony headphones would not connect, which makes sense to me because newer Sony headphones do not support AAC they only support SBC, AptX and LDAC even though some old Sony headphones did they removed it).
Also if you are not the type to read the instructions to learn how to use the product. I recommend you do not purchase it because you will likely not be able to figure it out and will end up returning them anyway. The instructions are very simple, but if you don't read how to follow the steps you will not figure it out on your own.
I use it to connect my bluetooth headphones with AAC codec to the DVD player. I plugged it into the "DVD Priority output" on the back of my DVD player (not the TV) using RCA to 3.5mm cable and I perceive no audio latency/lag (I recommend doing this way to reduce bluetooth audio latency). The way I understand it the tiny amount of AAC codec latency is very close to the latency it takes for the video signal to travel through the HDMI cable to the TV.
Product works as both transmitter and receiver (has 3.5mm input and output) and has 6 hours battery life so I charge it after watching 2 movies (roughly 4 hours use) and it keeps it working.
Included in the box is a short microUSB cable and 3.5mm cable. Bluetooth range is not as good as my Apple TV but that was expected because it's battery powered. With Apple TV I could walk to the bathroom without the audio cutting out, but the Bonelk starts cutting out in the bathroom.
Also even though I don't use it this way, this works as a Bluetooth receiver. So you can turn any 3.5mm connection only speakers into bluetooth speakers. I can't comment on latency in receiver mode but I would expect some latency and only recommend it for music. Compatibility should not be an issue in this mode because almost all phones will support SBC, AAC codecs.
Also kind of off topic so I will comment it here. But this solution for me was way cheaper than buying a cheap pair of RF/transmitter headphones for TV on sale such as this for $100.
https://www.amazon.com.au/Avantree-Ensemble-Bluetooth-Headph…
Most of you should have at least 1 pair of bluetooth headphones already, so I think this $24 solution to connect wireless headphones to older gear is a bargain. Also as mentioned in the post, it helps to get zero latency by connecting to it directly to the analog audio outputs on your "player" and not the TV.