New features and deprecations
* ENH: add key update_option for Well to roxar by jcrivenaes in https://github.com/equinor/xtgeo/pull/987
* ENH: Add gaussian smoothing method for `RegularSurface` and improve smoothing on surfaces with undefined values. by tnatt in https://github.com/equinor/xtgeo/pull/1002
* DEP: Issue deprecation warning for `xtgeo.plot` by mferrera in https://github.com/equinor/xtgeo/pull/1036
Backend code cleaning etc., and docs
* CLN: Add Dtyping to common/calc by ErichSuter in https://github.com/equinor/xtgeo/pull/978
* Enable OPM tests by eivindjahren in https://github.com/equinor/xtgeo/pull/986
* DOC: Update type hints section by janbjorge in https://github.com/equinor/xtgeo/pull/991
* CLN: Convert functionlogger to native null logger by janbjorge in https://github.com/equinor/xtgeo/pull/989
* CLN: Update code base to use py10 annotation by janbjorge in https://github.com/equinor/xtgeo/pull/993
* CLN: Install `_cxtgeo` in the root module by mferrera in https://github.com/equinor/xtgeo/pull/998
* CLN: Add .DS_Store to .gitignore by janbjorge in https://github.com/equinor/xtgeo/pull/1000
* CLN: Refactor roff `scan_keywords` to use roffio by mferrera in https://github.com/equinor/xtgeo/pull/992
* CLN: Add types xtgeo-dialog by janbjorge in https://github.com/equinor/xtgeo/pull/1001
* CLN: Add types to GridProperties by janbjorge in https://github.com/equinor/xtgeo/pull/1006
* CLN: Removed unused C code by mferrera in https://github.com/equinor/xtgeo/pull/1008
* CLN: Dynamically import matplotlib and pyplot by mferrera in https://github.com/equinor/xtgeo/pull/1009
* CI: Run Komodo tests in the RMS environment by mferrera in https://github.com/equinor/xtgeo/pull/999
* TST: xfail flaky OPM tests by mferrera in https://github.com/equinor/xtgeo/pull/1015
* CI: Fix Komodo ci script by mferrera in https://github.com/equinor/xtgeo/pull/1017
* CLN: Add types to _ecl_logi_head by mferrera in https://github.com/equinor/xtgeo/pull/1018
* CLN: Add types to grdecl_format by janbjorge in https://github.com/equinor/xtgeo/pull/1012
* CLN: Add types to grid_refine by janbjorge in https://github.com/equinor/xtgeo/pull/1013
* CLN: Add types to ecl_output_file by mferrera in https://github.com/equinor/xtgeo/pull/1019
* CI: Don't test against RMS environments by mferrera in https://github.com/equinor/xtgeo/pull/1021
* DOC: Update deprecated GridProperties examples by mferrera in https://github.com/equinor/xtgeo/pull/1022
* CI: Run CI nightly by mferrera in https://github.com/equinor/xtgeo/pull/1023
* TST: Update mypy settings - ignore errors file in xtgeo/grid3d by janbjorge in https://github.com/equinor/xtgeo/pull/1024
* CLN: Add types to ecl_inte_head by janbjorge in https://github.com/equinor/xtgeo/pull/1016
* CLN: Add types to _roff_parameter by mferrera in https://github.com/equinor/xtgeo/pull/1020
* DOC: Update Tips section in docs/contributing.rst by KetilN in https://github.com/equinor/xtgeo/pull/1032
* CLN: Move version file to version.py by mferrera in https://github.com/equinor/xtgeo/pull/1035
* CLN: Update GridProperty typing by mferrera in https://github.com/equinor/xtgeo/pull/1034
* CLN: Add types to gridprop_roxapi by tnatt in https://github.com/equinor/xtgeo/pull/1037
* CLN: Fix uninitialized variable in surf_get_z_from_xy.c by KetilN in https://github.com/equinor/xtgeo/pull/1041
* CLN: Add types to gridprop-import-roff by janbjorge in https://github.com/equinor/xtgeo/pull/1026
* CLN: Replaced OrderedDict instances with dict (1005) by abastola0 in https://github.com/equinor/xtgeo/pull/1043
* FIX: Union dtypes for Python 3.8 compatibility by mferrera in https://github.com/equinor/xtgeo/pull/1045
* CI: Run mypy on Python 3.8 as well by mferrera in https://github.com/equinor/xtgeo/pull/1048
* CLN: Port x_rotation_conv.c to python by janbjorge in https://github.com/equinor/xtgeo/pull/1030
New Contributors
* ErichSuter made their first contribution in https://github.com/equinor/xtgeo/pull/978
* tnatt made their first contribution in https://github.com/equinor/xtgeo/pull/1002
* abastola0 made their first contribution in https://github.com/equinor/xtgeo/pull/1043
**Full Changelog**: https://github.com/equinor/xtgeo/compare/3.4.2...3.5.0