Using "HtmlViewer-HtmlViewer-11.8" downloaded from
https://github.com/BerndGabriel/HtmlViewer, Lazarus SVN58059 and FPC 3.0.0 I didn't even get as far as you. Admittedly my system is a few months old now.
Personally I'd suggest you work with the code and bring it up to scratch. BerndGabriel has put a big hint there that he'd welcome changes from others :-)
If you got your "HtmlViewer-HtmlViewer-11.8" from elsewhere, please include this information. It's a big web out there, though I admit it didn't take me long to find BerndGabriel's version :-)
There's also a version of this code in Lazarus-CCR.
https://sourceforge.net/p/lazarus-ccr/svn/HEAD/tree/components/thtmlport/ Looks like an older branch (simply going on readme.html being dated 2009), but going on the comments on the last commit it compiles against FPC 3.0 So you could check out the two different projects, run a file diff - see what's changed to make the CCR version compile against FPC 3.0?
Or you could just try the version in Lazarus-CCR, might fit for your needs.
Or, and I should have thought of this first, you can try BerndGabriel's development version
https://github.com/BerndGabriel/HtmlViewer/tree/masterGoing on the Commit's, looks like it is tested under recent Lazarus... Always fun working with Development versions though, expect a few issues here and there though.
As for HTML viewer? You say you want a good solution, that's a little vague. I use TipHTMLPanel which is acceptable for my use (simple HTML help files).