For reading: Chrome with some free plugin
KamiPDF for reading pdf and annotation (sync with Google Drive). LuminPDF is good too. They are same thing, only different in brand name. If you just reading and highlight, annotation, and you have no need digital signing, OCR, … stuff, free is good.
hypothes.is for web annotation (highlight, annotated any web page, completely free)
For Thinking: Traditional pen and physical paper. You will typing your conclusion into paper writing tool anyway.
For writing: I use notion.so before move to Obsidian.
overleaf.com (similar to install latex, to publish PDF, free tier is good for solo writer. )
All my tool is either free, or free for personal use, or free tier have all useful feature.