My partner and I have a UA flight from DFW to IAH and we pre-purchased checked bags (1 bag for me and 2 for him). We have a separate award ticket on BR later that night in Business Class (IAH to TPE). I know that technically we should be able to get UA to check our bags all the way through. However, this is only our second time trying this (being based in DFW, I am much more familiar with AA rules), the first time we tried was in the summer of 2022 (DFW to IAH on UA, then separate IAH to SIN via Manchester on Singapore Business), and the UA agent flat out told me NO, she could not check the bags through. I pushed back and said I believe it's possible (since I had researched on Flyertalk in advance) but she insisted she couldn't. I was not confident enough to push the issue. We ended up collecting our bags and sitting landside for 4 hours for Singapore check in counters to open!! (we decided to take an earlier UA flight bc of possible inclement weather).

If the UA agent pushes back and says he/she can't check the bags through to TPE when we depart in a few weeks for TPE, should I just ask for a supervisor? Or ask him/her to call the help desk?

Additionally, just to be completely safe, does it have any impact on UA's ability to check the bags through to TPE if I do online check in on EVA's website? Or should I wait to do the online check in until after I checked in for our UA flight? If I do online check in for my EVA flight, I assume I just have to put 2 and 1 for our checked bags to match UA?

We would like to avoid having to sit landside for 3 hours waiting for the EVA check in counters to open. We are also planning on visiting the Polaris lounge for a light dinner. UA's last flight out of DFW gets us in to IAH around 6:45pm so we plan to head directly to the Polaris Lounge, unless we're forced to collect our bags again.

Thanks in advance for your help / advice!