According to Yeshiva.org which is what Rav Lau, the former chief rabbi of Israel (and former chief rabbi of Modiin, where he lives :-) ) psaked:

All the shuls follow this site.

https://www.yeshiva.org.il/calendar/timeprinciples

Here is a AI translation because I am lazy :-)

On the website we stated, in accordance with the ruling of the Rosh Yeshiva, Rabbi Zalman Baruch Melamed shlit”a, that in the summer, when the day is longer than 12 hours, nightfall is 18 seasonal minutes after the level sunset. In the winter, when the day is shorter than 12 hours, the time is 18 regular minutes after the level sunset. Thus, nightfall is never less than 18 minutes after sunset.

This is the time for the conclusion of the listed fasts, not including Tisha B’Av.

Regarding Tisha B’Av, one should be more stringent, since the Sages stated explicitly that its twilight period is forbidden. Therefore, the fast ends when the sun is 6.45° below the horizon; see Bein HaShemashot by Rabbi Y. M. Tukachinsky, p. 74.

Regarding Yom Kippur, the calculation for the end of the fast is the same as for the end of Shabbat.

Rabbi Deblitzky’s practice is that the minor fasts, including Yom Kippur Katan, end 15 minutes after sunset. For Yom Kippur and other matters, Rabbi Deblitzky follows the opinion of Rabbeinu Tam.

And as an aside, Candle Lighting for Modiin is 22 minutes is before Shkia.

but this isn’t how fast times are calculated in Israel. Can we have an option for that?