LTTnonstopdan
Saily is a relatively new eSIM service from the creators of NordVPN, but has become quite popular in a short amount of time. I've used it a fair bit around Europe and have found it to be well priced and easy to use, especially as you only install one eSIM once, and it is valid forever, even if you add more data and/or extra countries etc.
They're doing a summer deal currently which is 5% off plans over 10GB, and an extra 5% cash back in "Saily credits".
Use code "LTT" or "nonstopdan" for a 15% discount at check-out, although it's worth noting that each code is limited to one use per account. If you're doing a big trip, buy multiple countries or a larger amount of data so you get the maximum discount possible.
Just a reminder that prices on their website and in the app are all in USD.
Local sims, albeit more of a hassle, tends to be better deals.