I figured out a fix for this. Best guess is some directive logic is not playing nice with minicore.
I changed the library I2C directive to
#ifdef U8X8_HAVE_HW_I2C
# ifdef U8X8_HAVE_HW_I2C_TEENSY3
# include <i2c_t3.h>
# else
# include <Wire.h>
# endif
#endif /* U8X8_HAVE_HW_I2C */
and it works. Also posted over on Github Wire1 errors with 328P and minicore · Issue #2207 · olikraus/u8g2 · GitHub