What I have been doing to endure the extreme heat and being unwell so not wanting to sit in front of a computer:
Reading rpg rule books. On the OSR side, the Basic Fantasy Gaming rulebook is so good and PWYW or free. Options without bloating. I've been playing through a solo adventure to learn the rules, and my single hit point fighter miraculously made it home with some treasure by avoiding every fight and leaving early.
Microlite 20 is ultra simple, elegant, compatible with D&D 3.5e adventures and has a million variations (including "make a Star Trek TOS episode" and "Playing like it's D&D 0e." Might try to run a team of baby adventurers through a procedural dungeon.
I bought Mongoose Traveller (2e I think?) and some supplements in a Bundle of Holding a way back, but Humble currently has an irresistible deal to get, like, all of Classic Traveller for cheap. (The original three Little Black Books are always PWYW.) I'm slowly making my way through them, and meanwhile I have made five characters (let's take a moment to honour Pavlov, who died in character creation), mapped out a sector, and started to create six star systems in more detail. I did this with pen and paper, dice and ruler, but I think I will transfer solo play to PUM-C (Android) and use it to finally get to grips with Traveller, adding in more rules from supplements as I go, and reading the Adventures for an idea of how play works in practice.
PUM-C on an Android tablet is a great set-up. I split the screen so I have rulebooks in Read Era on the left, and journal and make rolls on the right. I need to get to grips with PUM-C too. Like Scrivener it seems to have so many useful features as to be overwhelming, but like Scrivener you can ignore most of them until you need them and gradually build up expertise. At least I hope so.
Right now I just use it for journalling, calculating dice rolls when I don't have my dice bag, as a basic Oracle, and to roll up random elements. But I want to learn the mapping features and plot construction and so forth.