How to approach zone practice if heart rate zones are completely inaccurate

I recently started training with a heart rate belt. However, my heart rate zones seem completely different from the information I could gather online.

First, I’m in my mid-thirties but have a maximum heart rate of 197, which is much higher than it should be. However, it seems for many people this can be the case.

Second, more importantly, my heart rate zones differ a lot from standard percentages. Cyclingweekly stated that 82-89% should be for efforts lasting a few minutes but it is ok for me to hold the mid-80s for several hours. 89% and above only works for a few minutes. I don’t seem to have any heart rate zone to target for a 20 minute effort.

Third, the indicator about speaking seems completely inaccurate. At 87%, speaking one sentence at a time (usually zone 2) is possible.

My question is how should I approach cycling practice based on zones if I fall out of the regular categories? I would also like to know possible reasons why the zones can be off, especially in case this relates to health issues or lack of training in some respect.