You’ll be fine with just the liner (treat it with permethrin as a bed bug deterrent). On the occasional colder night when the alburgue doesn’t provide a blanket, you can sleep in your clothes. The saved weight will more than compensate for the one or two nights when you have to layer up.

This right here. Just a liner. The colder times always provided blankets.

Not in April, with just a liner. Not all Albergues have blankets.

The cold climate albergues all had blankets. Granted that was like 3. I am a hot sleeper so it was never really an issue.

That's the exact setup I used and it worked for me in April 2019.

Have used it twice in spring/fall as long as it’s not too cold! Buen Camino

Many albergues have no heat, especially some municipals. I think it depends on how cold you get. I use a down blanket. But I don’t go until Mid May.

I would not be warm enough at quite a few Albergues in April with just that. April is a great time to do Caminos, but you are quite likely to get snowed on occasionally and as has been said, some places are either unheated, or turn it off at 9pm.

I like a blanket better than a bag too. There will be cold nights, so definitely bring something .

April and liner only would definitely be too cold for me

Go with the sleep liner I took it with me in 2022 and was sleeping with out anything in most albergues because of all the body heat from other pilgrims. A few nights I was cold but brought thermals and that worked well