I'm using pdflatex with book document class, and using the Sitx2 package, but when compiling a line with a math environment containing a \boldymbol command I get the error:
LaTex Font Warning: Font shape 'LS2/stix2ex/b/n' in size <10> not available (Font) Font shape 'LS2/stix2ex/m/n' tried instead on input line 52
Checking the Stix2 package manual (version 2.0.2), I see there are math alphabets (Chapter 4) which are not included by default: "TEX allows only 16 math alphabets to be used simultaneously, so not all of these alphabets can be used in one document. When the stix2 package is loaded, 12 math groups are allocated, with the 11 math alphabets that are marked above available by default, which leaves room for 4 other math groups to be allocated on demand when any of the other alphabets is used."
Question: how do I load (allocate) the alphabet required for \boldsymbol command? I suppose it would be the \mathbfit alphabet? Thanks.
EDIT Clarifying further, at request from comments: I need to load one of the alphabets of stix2 (Ch.4, as mentioned, not all are loaded by default). What is the specific alphabet I need to load to make
\boldsymbol work, and how do I do it?