There's a bit of a map for finding the English 'Re:Zero' web novel, but it's not super straightforward. The original Japanese text is on Kakuyomu and Shousetsuka ni Narou, obviously. For translation, the primary hub used to be Witch Cult Translations, which handled a massive chunk of the main story and many side stories. Their site is still up with all their work archived. However, their translation progress stopped a while back.
For more recent arcs, you'll have to look towards fan-driven efforts on places like the TranslationChicken website, which picked up after Witch Cult Translations paused. The quality's generally decent, though the update pace can be sporadic—depends entirely on the translator's free time and motivation. I'd also check the Re:Zero subreddit's wiki or pinned resources; the community there is pretty good at maintaining links to current projects.
It's a bit of a patchwork situation, honestly. You won't find a single, official, neatly packaged English web novel like you would on Amazon for a Kindle book. You're stitching together chapters from different translator sites, which means dealing with varying styles and sometimes long waits. I ended up reading most of Arc 6 across three different sites because the main translator for that section changed hands twice.
The lack of an official translation is a real pain point for western fans. You have to rely on the dedication of volunteers, which is amazing but inherently unstable. I wish Tappei or someone would just sanction an official platform, but until then, it's this digital scavenger hunt.