i've got a 12 year old Honda minivan with ~155k miles that now needs catalytic converters after i already put about $4k in it in the last year. And it's developed a shake that hopefully is just the rear tires needing balancing. It also needs tires, and at this age, probably shocks/struts. The wife wants to replace it with another Odyssey but they are hard to find right now at MSRP. Even with a declining market and rising interest rates, Honda's supply chain is still a mess and they have a very low inventory of cars available. At this point i'm planning on just clearing the engine code before the next inspection. 
I got a code reader/diagnostic tool for Christmas, was so excited to go out and do a deep dive into my yellow engine light!
It may be the same as yours - a P0420 code, "Catalyst System Efficiency Below Threshold Bank 1". I believe Bank 1 is the set of 3 cylinders in the rear of the engine, next to the firewall and not very accessible.
This light has come and gone for about a year now. Could be about 10 things wrong in theory, but some can be eliminated probably by logic. For example, an air intake leak would also affect Bank 2 in theory so not the likely culprit. Also, the O2 sensors seem to be working right - fluctuations in RPM's cause wild fluctuations in Sensor 1 (before the CAT) and Sensor 2 is perfectly level, which is desired. There are other diagnostics I can do with my $50 tool, but I'll skip the details. Most likely culprit is that at 192k miles, the CAT is just a bit dirty. I have from time to time run some engine cleaners through the system, which can cause carbon deposits to exit but get caught in the CAT.
Anyway, a very low cost strategy is to run a bottle or two of Cataclean through your system, which may be able to dissolve enough of the crud to get the CAT back in spec. My light went out just before I used the bottle, hasn't come back on but I have no way of knowing if it worked or not. But given the terrible cost of replacing the CAT seems a no brainer. BTW, aren't their 3 catalytic converters on our vehicles? One for each bank, and a third downstream, right?