My key takeaway: GP is right, going PV+HP is a safe default; at least around here(!!).
Unless you don't get money for selling excess power to the grid (batteries have become massively cheaper though) AND you have a gigantic roof. Even then, it's probably worthwhile investing more into the PV instead of getting solar thermal.
Of course this also depends on latitude.
Anecdata 1: Thermal solar installation between 49 to 50deg latitutide, central europe. My uncle's SFH.
Anecdata 2: We're currently adding PV+HP with cooling capacity to our own SFH and I would have loved thermal solar to be great, so I looked into this. (same rough geographic location).
During summer his thermal solar has great efficiency, but the heat tanks are already charged after 1 to 2h (that's what he said when we talked about it last summer). So the installation has at most 2h of say 80% efficiency (during low solar radiation in the morning!) and then another 8h of 0% since the heat can go nowhere. This also wastes the huge energy peak after noon. This means: The ratio between a days "total energy harvested" vs "total energy which reached the collectors" is even less than the arithmetic average of 16% efficiency. Of course they use hot water over day, but that only increases the efficiency a little bit. Especially considering the physically huge tanks they have installed (probably 1000l ballpark, and I think there are two of these?!).
Contrary in winter, the temperature differential between collector and fluid is so low that no heat/energy can be harvested at all. (At least for their installation and the winter temperatures around here).
Compare that to PV+HP: Any solar radiation is transformed to electricity with 22% efficiency.
In summer the COP [see sibling comments] is very high, so you can still quickly charge that hot water tank and then use the remaining energy harvested for your home or car, or sell it to the grid. Plus the hot water tank can be smaller (less losses!) since you don't need to "store" all the excess energy. E.g. we have 200l hot water and 200l buffer for heating (or actually: Defrosting the HP).
During winter the PV still produces some power that the HP can convert to heat (not too much and especially for less hours per day, but >0).
Maybe there are some sweet spots during spring and fall when solar thermal outperforms the PV+HP because it takes the whole day to charge the tanks. But then again when I installed my PV this spring, it produced >110% on a cool (16degC/60degF?), sunny day. So even during those seasons PV+HP are a tough competition.
Nice bonus for the PV+HP (that's what we're doing): If it's too hot in the summer, you can use the excess electricity to drive the HP in reverse mode for 7degC/44degF water temp in the "heating" system for active cooling. Due to condensation this requires dampproof insulation for the pipes, and convector units (sometimes also called "fan coils"?) to move enough air through the heat exchanger (car-like radiator) instead of traditional radiators or floor heating. But every convector can sink 1500W (5100 BTU?); for a room in a well-insulated house this can be enough.
Mind that our roof (south east + north west) has merely 60sqm per half, minus windows and other installations, so there is not too much space to add thermal solar. We get 0.07€ per kWh sold to the grid, so the excess PV mostly pays for itself. Battery is 11kWh usable, based on budget not "what we need" (data wasn't sufficient because we did all the renovations at once); this improves how much we can consume ourself; was more worthwhile than adding hot water tanks (we just can't consume that much hot water every day). We're also adding massive insulation to the 70y old house to slash heating requirements from >40MWh/y to something more sensible.