I want page numbers to start with document, not with front matter.

Tried insert, page, offset -5. It inserted one correct page number. There >250 pages. Otherwise, my text starts with page 6 and the front matter is all numbered.

Read these guidelines, then edit your question to improve it.

Never use offsets to try and skip page numbers, this is not their function.

See this somewhat similar question. The solution relies on use of page styles. If you don’t know what styles are, read the Writer Guide for an introduction.

Also ad this tutorial and this tutorial.